Agent Teams: "Surface not found" when creating new team after previous team shutdown

Environment

• cmux 0.63.1
• Claude Code (cmux claude-teams --dangerously-skip-permissions)
• macOS Darwin 24.6.0

Steps to Reproduce

1. Start session with cmux claude-teams
2. Create a team with TeamCreate
3. Spawn teammates with Agent tool (team_name parameter) → panes created successfully
4. Shutdown all teammates with SendMessage shutdown_request
5. TeamDelete to clean up
6. Create a new team with TeamCreate
7. Spawn teammates again → fails

Expected

New teammates should get new cmux panes after previous team is deleted.

Actual

All subsequent Agent(team_name=...) calls fail with:

Failed to create teammate pane: Error: not_found: Surface not found

cmux itself is healthy — cmux tree, cmux surface-health, cmux new-pane all work fine.
Manual pane creation via cmux new-pane --direction right succeeds.

Workaround

Restart the session (cmux claude-teams -c). First team in a fresh session works.

Analysis

After the first team's agent panes are closed via shutdown, claude-teams' internal surface mapping appears to retain stale surface UUIDs. New team creation tries to reference these stale surfaces instead of creating fresh ones.